5-PONTICS.pptx

Pontics

1. PONTICS. Definition . The pontic is the fixed partial denture component that replaces the missing natural tooth to restore function,esthetic and compatible with continued oral health and patient comfort. The pontic is attached to the retainer by a rigid connector such as solder joint or nonrigid connector in special cases such as key and keyway.

2. Design To peform proper pontic design careful analysis of the dimensions of the edentulous area (pontic space) mesiodistally,occlusocervically and buccolingually also the form and shape of the residual ridge must receive attention to provide hygienic requirements and prevent gingival irritation.

3. Pontic space . Tilting or drifting of the adjacent teeth into the edentulous space may occur reducing the available space for the pontic,so repositioning the abutments ortodontically when esthetics is important or modification of the abutments with complete coverage retainers is done.

4. Residual ridge contour. An ideally shaped ridge will be smooth to maintain plaque free. Patients who have irregular hyperplastic tissue,may need surgical removal of excess fibrous tissue. Bone resoption following tooth loss due to trauma may be present;this will affect aesthetic and biologic demands so;

5. a.)Augmentation with hydroxylapatite ships may be one solution. b.)Another solution is to create a roll of soft tissue labial to the pontic site.

6. Pontic classification. Pontic designs are classified into two general groups; those that contact the oral mucosa and those that do not. Pontic selection depends primarily on esthetics and oral hygiene. In anterior region where esthetics is a concern the pontic should be well adapted to the tissue to make it appear that it emerges from the gingiva.

7. In the posterior region (mandibular premolar and molar areas),esthetics can be compromised in the interest of designs that are more amenable to oral hygiene. 1.) Sanitary pontic. The primary design feature of the sanitary pontic allows easy cleaning because its tissue surface remains clear of the residual ridge.

8. A modified version of the sanitary pontic has been developed. Its gingival portion is shaped like an archway between the retainers. This geometry permits increased connector size while decreasing the stress concentrated in the pontic and connectors.

9. 2.)Modified ridge lap pontic. The modified ridge lap design overlaps the residual ridge on the facial surface (to achieve the appearance of a tooth emerging from the gingiva) but remains clear of the ridge on the lingual surface. To enable optimal plaque control , the gingival surface must have no depression rather it should be as convex as possible from mesial to distal(the greater convexity ,the easier the oral hygiene).

10. Tissue contact should resemble a letter T whose vertical arm ends at the crest of the ridge.

11. 3.)Conical pontic. Often called egg-shaped,bullet-shaped or heart-shaped, the conical pontic is easy for the patient to clean. It should be made as convex as possible ,with only one point of contact at the center of the residual ridge. This design is recommended for the replacement of mandibular posterior teeth where esthetics is a lesser concern.

12. The facial and lingual contours are dependent on the width of the residual ridge, a knife- edged residual ridge will necessitate flatter contours with a narrow tissue contact area. If used with a flat ridge, large triangular embrasure spaces around the connectors will result leading to food impaction.

13. 4.)Ovate pontic. Is the most esthetically appearing pontic design. Its convex tissue surface resides in a soft tissue depression or hollow in the residual ridge ,which makes it appear that a tooth is actually emerging from the gingiva.

14. Socket-preservation techniques should be performed at the time of extraction to create the tissue recess from which the ovate pontic form will emerge.

15. Biologic principles of pontic design This pertains to maintenance and preservation of the residual ridge, abutment and opposing teeth and supporting tissues. Factors of specific influence are: Pontic ridge contact Amenability to oral hygiene Direction of occlusal forces

16. 1. Ridge contact Pressure – free contact between the pontic and the underlying tissue is indicated to prevent ulceration and gingival inflammation. If any blanching on the gingiva is observed at try-in, the pressure area should be eliminated until tissue contact becomes passive. When the pontic rests on the mucosa, some ulceration may appear. In the anterior region of the mouth where esthetics is important, the pontic should contact the gingival tissue on the labial or buccal surface to give a more natural appearance. Special care must be paid to the gingival surface of the pontic to prevent tissue impingement and ulceration at the contact area. In the posterior region, more attention should be paid to occlusion, function and hygiene.

17. According to the shape of the gingival surface and its relationship with the underlying mucosa, the p ontic may be classified into two groups: Mucosal contact R idge lap Modified ridge lap Ovate Conical b. Non – mucosal contact Sanitary( hygienic) Modified sanitary ( hygienic)

18. With mucosal contact types, the excellent hygiene habits must be developed by the patient, and the use of proxy brushes, pipe cleaners, super floss and dental floss are highly recommended. The pontic that overlaps the buccal and lingual sides of the residual ridge is called saddle shaped pontic, should be avoided because of its concave gingival surface which cannot be easily cleaned by the patient.

19. 2. Dental plaque The main cause of ridge irritation is the release of toxins from microbial plaque which accumulate between the gingival surface of the pontic and the residual ridge. To enhance plaque control, the patient must perform efficient oral hygiene techniques especially on the gingival surface of the pontic. The shape of the gingival surface of the pontic, in relation to the ridge and the material used for pontic fabrication will affect dental plaque control.

20. 3. Pontic materials The materials used should provide good esthetics when needed, biocompatibility, rigidity, strength to withstand occlusal forces and longevity. FPDs should be as rigid as possible because any flexure during mastication or Para function may cause pressure on the gingiva and cause fractures of the veneering material. Occlusal contacts should not fall on the junction between metal and porcelain during centric or eccentric tooth contacts , nor should a metal ceramic junction occur in contact with the residual ridge on the gingival surface of the pontic.

21. Two important factors in biocompatibility of materials: The effects of the materials The effects of surface adherence Glazed porcelain- generally considered the most biocompatible of available pontic materials. The critical factor is the material’s ability to resist plaque accumulation. Well polished gold- smoother, less prone to corrosion, less retentive of plaque than unpolished or porous casting. Although glazed porcelain looks very smooth, under a microscope, its surface shows many voids and is rougher than polished gold or acrylic resin. Nevertheless, highly glazed porcelain is easier to clean than other materials.

22. 4. Occlusal forces Reducing buccolingual width of the pontic by as much as 30% has been suggested as a way to lessen occlusal forces on and thus the loading of abutment teeth. This practice continues today, though with little scientific basis. Critical analysis show that forces are lessened only when chewing food of uniform consistency. Potentially harmful forces are more likely to be encountered if a FPD is loaded by accidental biting on a hard object or parafunctional activities like bruxism. These forces are not reduced by narrowing the occlusal table.

23. In some cases, narrowing the occlusal table may impede or preclude the development of a harmonious and stable occlusal relationship. Like in a malposed tooth, it may cause difficulties in plaque control and may not provide proper cheek support. This is why pontics with normal occlusal widths on the occlusal thirds are recommended.

24. MECHANICAL PRINCIPLES

25. Its influenced by Choice of material Tooth preparation Framework design Occlusion Interference of the above factors will result to fracture of the restoration or displacement of retainers

26. Long-span posterior FPDs are particularly susceptible to mechanical problems. T here is significant flexing from high occlusal forces and because the displacement effects increase with the cube of the span length . Therefore, evaluating the likely forces on a pontic and designing accordingly are important. For example, a strong all-metal pontic may be needed in high-stress situations rather than a metal-ceramic pontic , which would be more susceptible to fracture. When metal-ceramic pontics are chosen, extending porcelain onto the occlusal surfaces to achieve better esthetics should also be carefully evaluated. In addition to its potential for fracture, porcelain may abrade the opposing dentition if the occlusal contacts are on enamel or metal.

27. Available pontic material 1-prefabricated porcelain pontis ; once used but are no longer used 2-metal ceramic pontic;is strong easy to clean and natural appearing

28. 3-resin veneered pontics ; used as long term restoration because they have low abrasive resistance , they have dimensional change due to low water absorption and thermo cycling. The resin must be retained to underlying metal by mechanical means due to its dimensional change Leakage may o ccur leading to discoloration and failure of bond

29. Advantages of resin Easy to manipulate Easy to repair Do not require high melting range alloys that are needed for metal ceramic

30. 4-fiber reinforced composite resin pontics It can be used without a metal substracture . The substructure matrix of impregnated glass or polymer fiber provides structural strength It has good marginal adaptation and esthetics.

31. 2;PROPER FRAMEWORK DESIGN 2. The metal surfaces to be veneered must be smooth and free of pits. Surface irregularities will cause incomplete wetting by the porce lain slurry, leading to voids at the porcelainmetal interface that reduce bond strength and increase the possibility of mechanical failure. 3. Sharp angles on the veneering area should be rounded. They produce increased stress concentrations that can cause mechanical failure. 4. The location and design of the external metalporcelain junction require particular attention.Any deformation of the metal framework at the junction can lead to chipping of the porcelain . For this reason, occlusal centric contacts must be placed at least 1.5 mm away from the junction. Excursive eccentric contacts that might deform the metalceramic interface must be watched carefully.

32. ESTHETIC PRINCIPLES An esthetically successful pontic will replicate the form , contours, incisal edge, gingival and incisal Embrasure Special attention should be paid to the contour of the labial surface as it approaches the pontic -tissue junction to achieve a " natural " appearance.

33. This cannot be accomplishedby merely duplicating the facial contour of themissing tooth, because after a tooth is removed, thealveolar bone undergoes resorption and/or remodeling.If the original tooth contour were followed,the pontic would look unnaturally long incisogingivally . To achieve the illusion of a naturaltooth , an esthetic pontic must deceive observers into believing they are seeing a natural tooth.

34. LIGHT AND SHADE;In normal situations, light falls from above, and an object's shadow is below it. Unexpected lighting or unexpectedly placed shadows (Fig. 20-33) can be confusing to the brain. Because of past experience,the brain "knows" that a tooth grows out of the gingiva,and it therefore "sees" a pontic as a tooth unless telltale shadows suggest otherwise. Special care must be taken when studying where shadows fall around natural teeth, particularly around the gingival margin . If a pontic is poorly adapted to the residual ridge, there will be an unnatural shadow in the cervical area that looks odd and spoils the illusion of a natural tooth

35. Correct incisogingival height is critical to esthetic pontic design. A, Esthetic failure of a four-unit FPD replacing the right central and lateral incisors. The pontics have been shaped to follow the facial contour of the missing teeth, but because of bone loss they look too long. B, The replacement FPD. Note that the gingival half of each pontic has been reduced. Esthetics is much improved. C, This esthetic failure is the result of excessive reduction.

36. 2;propotion Teeth are considered to be propotional if all of them are in proportion both the pontcis and adjacent teeth 3-balance Position of midline should be placed properly

37. with moderately severe bone resorption,obtaining a natural appearance by exaggerated contouring of the pontics may still be possible. In areas where tooth loss is accompanied by excessive loss of alveolar bone, however, a pontic of normal length would not touch the ridge at all.One solution is to shape the pontic to simulate a normal crown and root with emphasis on the cementoenamel junction . The root can be stained to simulate exposed dentin . Another approach is to use pink porcelain to simulate the gingival tissues. However, such pontics then have considerably increased tissue contact and require scrupulous plaque control for long-term success

38. Abnormal mesiodistal width Edentulous space may be greater or smaller than the width of the contralateral tooth,due to tooth movement that occurred when a tooth was removed and not replaced ,this should be corrected by; 1;Orthodontic treatment 2;by changing the relative positions of the mesiofacial and distofacial line angles and hence the overall surface shape and contour and light reflection between line angles